Sheet detector



April 19% J. E. VANDEMAN 3117631 SHEET DETECTOR Filed May 5, 1963lNVENTbR JACK 1 VAAIDM4N ATTORNEY United States patent @fiice 3,1753%Patented Apr. 6, 1955 3,176,981 SHEET DETECTOR Jack E. Vandeman, Berea,flhio, assignor to Harris-Intertype Corporation, Cleveland, Ohio, acorporation of Delaware Filed May 6, 1963, Ser. No. 278,252 8 Claims.(Cl. 271-57) This invention relates to mechanism for detectinginaccuracies in the positions of sheets in a travelling lapped streamand in the thickness of various sections of the stream of sheets.

In the type of sheet feeder in which sheets are fed in underlappedstream fashion to a printing press or the like, the top surface of thestream has alternate thick and thin sections moving past a given pointor points. The thick and thin sections are formed by the way the sheetsare lapped. For purposes of this application, I prefer to designatethose sections where an edge of a sheet overlaps one or more othersheets as lap sections, and those portions of the stream of sheetsbetween the lap sections as stream sections.

Sheet feeders which form the stream and move it along a feed table mustpresent the lead edge of each sheet to registering mechanism with veryaccurate timing in relation to the printing press. If, for any reason, asheet is advanced or retarded beyond certain limits from its properposition prior to reaching the sheet registering mechanism, seriousconsequences to the machinery may result, such as is well understood bypersons acquainted with the art. In addition, if a double layer ofsheets (e.g., two sheets stuck together and feeding as one) is fed intothe machine, and if such double sheet is on time at the sheetregistering mechanism, serious damage can also result to the machine.For example, in the case of a lithographic printing press having arubber blanket printing against imprint receiving stock, double sheetsfed at the same time through a printing nip may smash the rubber blanketand prevent its further usefulness.

Still another cause of occasional trouble, particularly when feedingrelatively thick board material, is that mill scraps or small chunks ofsheet material are sometimes left in the pile accidentally and are fedwith the stream of sheets into the machine. This can also cause blanketsmash or other damage, depending on the type of ma- I or undesirableconditions in a travelling stream of lapped sheets in all sections ofthe stream.

Another object of this invention is to enable detection of inaccuraciesin a stream of sheets in the thinner or stream sections between spacedlap sections.

Other objects and advantages will be apparent from the followingdescription in which reference is made to the accompanying drawing.

In the drawing, I present a schematic illustration of my sheet detectingmechanism and preferred form of control circuit operating upon a streamof underlapped sheets.

According to the preferred embodiment of my invention, a member isadapted to ride on the top of a stream of underlapped sheets havingalternate thick lap and thin stream sections formed in the direction ofsheet travel by the manner in which the sheets are lapped. This memberis arranged to continuously detect any stream thickness greater than thethickness of the lap section. In addition, the same or some other memberwill be arranged to detect any thickness of sheets greater than thestream or thinnest portion of the stream of sheets, but is adapted toprovide such latter detection only during the time the member is ridingupon what is normally supposed to be the thin stream section.

Referring now to the drawing, a stream of sheets may be fed from rightto left along a feed table 10 by means of thin drive belts or tapes 11,a plurality of which are spaced laterally with respect to the directionof travel of the stream of sheets. The belts are conventionallycontinuous and uni-directional, and are trained over rollers havingtheir upper peripheries approximately flush with the top surface of thetable 10 and located at each end of the table. The stream is formed by asheet feeder (not shown) which presents sheets to take-out rollers (notshown) just prior to their being placed onto the belts 11. At the leftend of the table 10, there is conventionally found a sheet registeringmechanism (not shown) which temporarily arrests each sheet in turn toregister it along its front edge and one side edge. After registration,each sheet is fed into a sheet handling machine (not shown) such as aprinting press. Since the mechanisms for forming the stream, registeringthe sheets, and handling the sheets through the machine are not a partof the present invention, they will not be further described except tohave it understood that these various mechanisms are adapted to havetheir operation stopped when the sheet detection mechanism of thepresent invention detects an improper condition of a certain type in thestream of sheets. The physical detection of such condition is preferablyprovided by a roller 12, which through circuitry 13 to be describedactuates a solenoid 14 to perform a control function which results inthe tripping or stopping of the aforementioned mechanisms.

It will be noted in the drawing that the sheets in the stream havesections of double thickness followed by sections of triple thickness.The roller 12 is shown riding on a latter such section. As previouslymentioned, I will herein refer to the thick sections as lap sections andthe thin sections as stream sections. While my invention is demonstratedin connection with a stream varying in thickness from between two andthree sheets, it is applicable also to other differences in numberbetween the lap and stream sections.

As shown, roller 12 is riding on a lap section on the top of a sheet Sand has between it and the tapes 11 the thickness of two additionalsheets, S and S This roller 12 is urged toward the table 10 by gravityand a spring 15 acting upon an arm 16 of a lever 17 rotatably supportingthe roller 12. The lever 17 is pivoted at 18. It will be noticed thatthe roller 12 will ride up and down on the alternate lap and streamsections. It has been customary in the past to provide such means fordetection only of multiple sheets, i.e., an extra sheet thickness, andthis extra sheet could be detected only in a lap section. If a sheet wasout-of-time in one direction, e.g., sheet S being advanced an inch tothe left of its proper position, the roller 12 as previously utilizedhad no way of determining this fact. This problem had to be corrected byanother detector or sensor, ordinarily located directly adjacent thesheet registering mechanism. This other detector would sense only earlysheets, i.e., those which were advanced in their position of the streamof sheets. It will be seen that the present invention, in addition tosensing multiple sheets or scraps located in the lapped sheets, alsoenables accomplishment of early sheet direction. It also providesdetection of late sheets by virtue of the fact that a sheet which isretarted at its lead edge will also have a tail edge which is likewisepositioned rearwardly of its normal position and thus presented from thelap section into the stream section immediately to the rear thereof. Themanner of accomplishing this detection will be discussed presently.Absent sheets are not detected by the shown apparatus, but such can beeasily provided by actuating a switch closed by arm 16 when only asingle sheet thickness is found in the stream section of the example inthe drawing.

Sheets in correct time The operation of the sheet detecting mechanismwhen the stream of sheets is of the correct thickness and properlyformed and all sheets are in proper position as shown in the drawing isas follows: At the time that the roller 12 is riding on a lap section,an adjustable screw 19 threaded in the arm 16 is adapted to engage thebutton of 'a normally open limit switch 20 to close the switch. Thisswitch is in series circuit with a limit switch 21 operated by anadjustable cam 22 driven in timed relation with the stream. It will beseenthat the limit switch 21 is open when roller 12 isriding on a lapsection, and consequently closing of the switch 20 has no immediateeffect upon the solenoid 14 in series with the switches 20 and 21. Asthe stream of sheets moves to the left in the drawing and the roller 12drops off the tail edge of sheet S the roller will engage the streamsection immediately behind the sheet S This stream section is shown ashaving but two sheet thicknesses, namely sheetsyS and S The adjustablescrew 19 which closed the switch 20 while the'roller 12 was riding on aproper thickness lap section is arranged to disengage the button of thelimit switch 29 when but two sheets, i.e., a stream section, arepresented to the roller 12. am 22 will then enable limit switch 21 to beclosed during the entire time a stream section is presented to theroller 12, but the factthat switch 20 is no longer closed during thistime prevents operation of the solenoid 14. It will be seen therefore,that screw 19 operates switch 20 once for each cycle, the switch 20being closed during the lap portion of a cycle and being open during thestream portion of the cycle. So long as the sheets remain properlypositioned and so long as double sheets or scraps are not fed into thestream of sheets, the mechanism will continue to operate as justmentioned and the stream of sheets will continue to be fed unlessstopped by the operator or certain other mechanisms in conventionalfashion. 7

Double or multiple sheets ness increased by the extra sheet arrives atthe roller 12, i

this will cause the lever 17 to pivot clockwise about pivot 18 through agreater angle than normal. This causes an adjustable screw 23 carried byarm 16 to engage the button of a normally open'limitswitch 24 to closethe switch. The adjustable screw 23 is set to detect any thicknessgreater than the proper thickness of a lap section by the additionalangular movement of arm 16. When switch 24 is closed, it willimmediately actuate solenoid 14, bypassing the opened limit switch 21 toperform its customary control function, e.g., tripping of the press. Theoperator will thereafter correct the stream on the table or will removethe double sheet and all sheets to the left of it so that operation maybe resumed. 1

Fast sheet 7 Let us assume now that a sheet has its lead edge presenteda few inches in advance of its proper position in a stream of sheets.(This example applies also to double sheets in which the leading edgesof the sheets are staggered.) For instance, sheet S may have its leadedge somewhat to the left of its position shown in the drawing, andwithin the range of time during which switch 21 is permitted to beclosed by the 0am 22,'as designated by the space entitled Cam SwitchClosed in the drawing. As the roller drops from the lap section as shownonto the following stream section, switch 20 will open, since screw 19is adjusted to close switch 20 only when more than the thickness of astream section is engaged by the roller able feature;

.4 12. When the lead edge of the out-of-time fast sheet S now comesopposite the'roller '12, the roller will immediately reclose switch 20.The timing of this reclosing occurs while the cam switch 21 is permittedto be closed by cam 22, thus causing a circuit through both switches 2dand 21, and an actuation of solenoid 14. The solenoid performs itsordinary control function of tripping the machinery. The stream ofsheets may again be fed only after the incorrectly timed sheets arecorrected or removed.

Late sheet IfsheetS is late, i.e., retarded from its proper position inthe stream of sheets, the trailing edge of that sheet will extendrearwardly of its normal position. Switch 20 is set to close as soon asa lap section comes under the roller 12. Since the trailing edge ofsheet S extends rearwardly of its'proper position, however, switch 20will remain closed until roller 12 drops off the trailing edge of sheetS When the cam 22 then permits the limit switch 21 to be closed whileroller 12 is still riding on the lap section, a circuit will beestablished through switches 20 and 21, thus energizing solenoid 14 asin the previous example. The late sheetwill therefore appear as an addedsheet thickness in the early portion of a stream section, during theperiod designated Cam Switch Closed. e i

' Scrap detection When a stream of underlapped sheets is properlyformed, the leading edges of sheets will be equidistantly spaced. Thisspacing is maintained in conventional sheet feeding mechanism eventhough the mechanism is later arranged to feed sheets of a differentlength. Assume that sheets 25" in length have been fedand the printingor other job has been completed. If sheets 23 in length are now to befed to the press, the lead edges of each sheet will be spaced the sameas they were for 25" sheets, but the trailing edge of each sheet will be2" to the left of their positions shown in the drawing. This means thatthe lap section will be shortened and the stream section lengthened. Tocompensate for this, the cam 22 may be adjustable by providing a portion25 which must be moved angularly to cause earlier closing of the limitswitch 21 so that proper detection may be accomplished during the fulllength of time corresponding to the now-lengthened stream section.Obviously, the cam can be likewise adjusted in the opposite directionwhen longer sheets are fed. 7

Although I have shown the switch 21' as being operated by an adjustablecam, it is obvious that other mechanical or electrical means can beutilized to provide this adjust- The type of mechanism to be used willdepend somewhat upon the range of sheet lengths for which the mechanismis adapted. It is theoretically possible that the lap section of astream may occupy anywhere from 5 to 355 of a cycle of the mechanism foroperating the switch 21.

While I have simply illustrated my invention as embodying a singleroller 12, I wish it to be understood that this roller may be of narrowwidth or of the full width of the stream of sheets. 'Full width is infact preferable when scrap detection is a problem. When roller 12 is thefull width, I may wish to supply levers 17 and the various partsoperated thereby at each end of the roller so that if either lever17 isoperated, the solenoid 14 will be energized.

While I prefer that a single roller 12 be used to operate both switches2t: and 24, it should be understood that a separate roller may be usedto operate each switch. One roller may perform only to close switch 2dwhen the thickness of the stream of sheets is greater than the properthickness of a lap section, and the other to actuate switch 29 to closewhenever the thickness of a stream section is greater than its properthickness.

Although I have demonstrated the switches 20 and 24 as being normallyopen, I may also use normally closed switches which are positioned onthe opposite side of arm 16 and held open during proper feedingconditions. Then, when a scrap, double, early or late sheet is detected,a clockwise movement of lever 17 will cause the normally closed switchesto close, this being permitted by movement of the arm 16 away from itsposition of holding these switches in their open conditions.

Various other changes may be made in the details of the inventionwithout departing from the spirit and scope of the claims.

Having thus described my invention, I claim:

1. In a sheet detecting mechanism,

a feed table,

means for transporting sheets in lapped stream fashion along said feedtable to provide said stream with alternate thick lap and thinner streamsections in the direction of travel of said sheets,

a member riding in contact with the top of said stream of sheets andadapted to alternately move up and down on the lap sections and streamsections respectively,

means performing a control function upon detection of an excessthickness of sheets being presented to said member when riding on eitherof said sections of said stream of sheets,

a first switch in circuit with said control means and adapted to beclosed in response to movement of said member upon detection of anexcess sheet thickness in a lap section of said stream,

a second switch adapted to be closed in response to movement of saidmember upon detection of an excess sheet thickness in a stream section,

means cyclically timed with the travel of sheets along said table,

and a third switch adapted to be opened by said timed means during aperiod of time in which the member is normally riding upon a lap sectionof the stream of sheets and adapted to be closed by said timed meansduring a period of time in which the member is normally riding upon astream section of said stream of sheets,

said second and said third switches being in series circuit with saidcontrol means, whereby said second switch can function to operate saidcontrol means only during that portion of a cycle when the memher isriding u on a section which is normally a stream section.

2. The invention set forth in claim 1 wherein said timed means isadjustable to enable varying of the periods of time of each cycle duringwhich said third switch is closed and opened.

3. In a sheet detecting mechanism,

a sheet support,

means for transporting sheets in lapped stream fashion along saidsupport to provide said stream with alternate thick lap and thinnerstream sections in the direction of travel of said sheets,

means sensing the thickness of said stream of sheets in both said lapand said stream sections,

means performing a control function upon detection of an excessthickness of sheets presented to said sensing means in either of saidsections,

d a first switch in circuit with said control means and adapted to beclosed by said sensing means upon detection of an excess sheet thicknessin a lap section of said stream, a second switch adapted to be closed bysaid sensing means upon detection of an excess sheet thickness in astream section of said stream, means cyclically timed with the travel ofsheets along said support, and a third switch adapted to be opened bysaid timed meansduring a period in which the sensing means is normallysensing a lap section and adapted to be closed by said timed meansduring a period of time in which the sensing means is normally sensing astream section, said second and third switches being in series circuitwith said control means, whereby said second switch can function tooperate said control means only during that portion of a cycle when thesensing means is sensing a section which is normally a stream section.4. The invention set forth in claim 3 wherein said timed means isadjustable to enable varying of the periods of time of each cycle duringwhich said third switch is closed and opened.

5. In a sheet detecting mechanism, a sheet support, means fortransporting sheets in lapped stream fashion along said support toprovide said stream with alternate thick lap and thinner stream sectionsin the di-' rection of travel of said sheets,

means sensing the thickness of said stream in said thinner streamsections,

means for performing a control function upon detection of an excessthickness of sheets presented to said sensing means,

switch operating means timed with the travel of sheets along saidsupport,

a first switch independent of said switch operating means, said firstswitch being adapted to be closed by said sensing means upon detectionof an excess sheet thickness in a stream section of said stream,

and a second switch operated by said switch operating means to open eachtime said sensing means is norrnally sensing a lap section and to closeeach time said sensing means is normally sensing a stream section,

said switches being in series circuit with said control means, wherebysaid first switch can function to operate said control means only duringthat portion of a cycle when the sensing means is sensing a sectionwhich is normally a stream section.

6. The invention set forth in claim 5 wherein said timed switchoperating means is adjustable to enable varying of the periods of timeof each cycle during which said second switch is closed and opened.

7. The invention set forth in claim 5 wherein said sensing meanscomprises a member normally riding in contact with the top of saidstream of sheets.

8. The invention set forth in claim 5 including a third switch incircuit with said control means and adapted to be closed by said sensingmeans upon detection of an excess thickness in a lap section of saidstream.

References Cited by the Examiner UNITED STATES PATENTS 1,738,180 12/29Frazier 270-56 2,551,364 5/51 Coakley 2'7157 2,632,545 3/53 Schubert27l-57 X 2,665,907 1/54 Ribich 27l57 ROBERT B. REEVES, Acting PrimaryExaminer.

RAPHAEL M. LUPO, SAMUEL F. COLEMAN,

Examiners.

5. IN A SHEET DETECTING MECHANISM, A SHEET SUPPORT, MEANS FORTRANSPORTING SHEETS IN LAPPED STREAM FASHION ALONG SAID SUPPORT TOPROVIDE SAI STREAM WITH ALTERNATE THICK LAP AND THINNER STREAM SECTIONSIN THE DIRECTION OF TRAVEL OF SAID SHEETS, MEANS SENSING THE THICKNESSOF SAID STREAM IN SAID THINNER STREAM SECTIONS, MEANS FOR PERFORMING ACONTROL FUNCTION UPON DETECTION OF AN EXCESS THICKNESS OF SHEETSPRESENTED TO SAID SENSING MEANS, SWITCH OPERATING MEANS TIMED WITH THETRAVEL OF SHEETS ALONG SAID SUPPORT, A FIRST SWITCH INDEPENDENT OF SAIDSWITCH OPERATING MEANS, SAID FIRST SWITCH BEING ADAPTED TO BE CLOSED BYSAID SENSING MEANS UPON DETECTION OF AN EXCESS SHEET THICKNESS IN ASTREAM SECTION OF SAID STREAM, AND A SECOND SWITCH OPERATED BY SAIDSWITCH OPERATING MEANS TO OPEN EACH TIME SAID SENSING MEANS IS NORMALLYSENSING A LAP SECTION AND TO CLOSE EACH TIME SAID SENSING MEANS ISNORMALLY SENSING A STREAM SECTION, SAID SWITCHES BEING IN SERIES CIRCUITWITH SAID CONTROL MEANS, WHEREBY SAID FIRST SWITCH CAN FUNCTION TOOPERATE SAID CONTROL MEANS ONLY DURING THAT PORTION OF A CYCLE WHEN THESENSING MEANS IS SENSING A SECTION WHICH IS NORMALLY A STREAM SECTION.